1. Field of the Invention
The invention relates to measuring the mechanical properties of biological tissues in general and to measuring strain in tendons and ligaments in particular.
2. Description of the Related Art
A variety of methods exist for measuring the strain of tendons and ligaments such as transducer methods, marker-tracking methods, and medical imaging methods. Transducer based methods typically utilize displacement sensors that are physically attached to the tissue of interest and convert the mechanical energy of displacement (i.e. work) into an electrical signal that can be interpreted by a computer. Examples of such displacement sensors include extensometers, liquid metal strain gauges, Hall effect sensors, and Differential Variable Reluctance Transducers. Marker-tracking based techniques utilize basic continuum mechanics principles to compute the regional strain tensor between groups of “markers” identified on planar or volumetric images of the tissue. These markers can either be externally applied to the tissue or alternatively identified from morphological features.
Marker-tracking techniques have grown more sophisticated and easier to implement in recent years with the development of automatic image digitization and digital image correlation techniques. Medical imaging based strain measurement via ultrasonography and MRI provide non-invasive techniques for measuring in vivo strain, however they can impose a significant cost burden on the researcher.